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Friendly bacteria: do they do what's promised?

Bacteria designed to boost health, rather than make you sick? It sounds counterintuitive, but it’s one of the hottest food trends today. Products containing probiotics, also known as “friendly” bacteria, similar to those found in the human digestive system, are spreading like germs on grocery store shelves.

Millions of friendly bacteria live in the intestinal tract, helping keep “unfriendly,” illness-causing bacteria at bay. Scientists believe that illness results when the unfriendly bugs start to take over. Those “bad” bugs have been implicated in many common digestive problems including inflammatory bowel disease and irritable bowel syndrome.

In an effort to cash in on America’s obsession with health, major food manufacturers like Dannon, Kraft and Nestle are marketing everything from supplement pills, yogurts, cheeses, cereals – even baby formula and chocolate – containing friendly bacteria that promise to regulate your digestive system and boost immunity. But do they really work?

“There are some studies that show taking probiotics to reduce antibiotic diarrhea can be beneficial,” says Korzenik. And, in large doses, probiotics have shown to significantly reduce symptoms in patients diagnosed with pouchitis. Pouchitis is inflammation of an internal pouch created in patients who have part of their colon removed to treat ulcerative colitis. However, research shows the bacteria is only slightly helpful for patients with ulcerative colitis. For those suffering from Crohn’s disease, the studies have been largely negative.

Korzenik explains that “probiotics” is a general term, much like “medication.” There are hundreds of different probiotic bacteria, each with a specific purpose. “So, when you go to your health food store or supermarket, and you see something that has a probiotic in it, it really depends on the subtleties of the dose, the preparation and the reason for taking it,” says Korzenik. He also cautions that many products haven’t been rigorously tested.

There are also “prebiotics,” which contain fiber and other nutrients that feed probiotic bacteria. Many products found on store shelves or dairy cases claim this probiotic food source can improve digestion.

For most patients who use probiotics or prebiotics and report benefits, it is likely they are experiencing a placebo effect, Korzenik says. “It’s an area of great hope and promise, but so far that promise hasn’t been realized.”

But that may soon change; the National Institutes of Health (NIH) is now investigating the bugs and has declared the study of gastrointestinal bacteria and probiotics a major research initiative. The Institute’s Human Microbiome Project will use genomic technologies to examine the role bacteria, fungi and other microbes play in the human body.

“The human microbiome is largely unexplored,” said NIH director Elias A. Zerhouni, M.D. “It is essential that we understand how microorganisms interact with the human body to affect health and disease. This project has the potential to transform the ways we understand human health and prevent, diagnose and treat a wide range of conditions.”

The Human Microbiome Project will begin by sequencing 600 microbial genomes, completing a collection that will total some 1,000 microbial genomes and providing a resource for investigators interested in exploring the human microbiome. Researchers will then use new laboratory technologies to characterize the microbial communities present in samples taken from healthy volunteers. The samples will be collected from five body regions known to be inhabited by microbial communities: the digestive tract, the mouth, the skin, the nose and the female urogenital tract.

In the meantime, Korzenik is investigating what types of bacteria are present in the digestive tract of patients with inflammatory bowel disease. Bacteria found in the gut, also referred to as gut flora, play a significant role in the health of the digestive tract. “Hopefully over the next 5–10 years as we understand flora better, we’ll have a much better sense of what’s wrong, what’s altered in flora and how we can counter that to make more effective therapies,” notes Korzenik.

The good news about “good” bacteria is that taking them can’t hurt you. However, Korzenik adds that a good diet is more important to overall health than taking any particular probiotic.